Overview DNA CODIS• DNA cannot determine how it was left on the evidence • Sometimes complex mixtures are not interpretable • Limited samples can yield incomplete profiles There

Overview

The Forensic DNA section is staffed by 23 scientists comprised of DNA lab analysts, DNA interpretation analysts, CODIS administrators, and supervisors. This unit processes several thousand requests for analysis each year.

Evidence that has been screened for biological material by the Evidence Screening Section (ESS) and determined suitable for DNA processing is then passed to the DNA lab analyst to generate a DNA profile through a four-step process. The DNA interpretation analyst then evaluates the DNA profiles, compares any suitable profiles, generates a report, and enters any eligible profiles into CODIS (see below for more information about CODIS).

The CODIS Administrator is the central point of contact in the laboratory for CODIS and serves as the gatekeeper for the DNA records entered into CODIS. As part of their gatekeeper function, the CODIS Administrator is responsible for performing, or overseeing the performance of but not limited to, the following: Assists with compliance with Quality Assurance Standards for Forensic DNA Testing Laboratories relevant to CODIS, maintaining system records and user information, reporting monthly hit counts and updating match dispositions, evaluating CODIS generated matches, complying with CODIS security requirements, and maintaining and submitting all paperwork required for NDIS participation. The Administrator has the authority to terminate the laboratory’s participation in CODIS in the event of a problem until the reliability of the computer data/profiles can be assured.

Overview 1DNA 2-4Extraction 2Quantification 2Amplification 2Characterization 2CODIS 5Success Stories 5-6

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DNA (Deoxyribonucleic Acid)

DNA is the blueprint of life or the genetic make-up that makes each individual unique and identifiable. Only identical twins have the same DNA. It is inherited directly from a person’s biological parents – half of an individual’s DNA comes fromthe father and half from the mother.

There are some limitations to DNA analysis:• DNA cannot determine when a person was at the crime scene• DNA does not determine consent in sexual assault cases• DNA cannot determine how it was left on the evidence• Sometimes complex mixtures are not interpretable• Limited samples can yield incomplete profiles

There is a four-step process to DNA analysis – extraction,quantification, amplification and characterization of amplified DNA.

ExtractionVarious chemicals are used to break apart the cells and isolate the DNA within a liquid buffer. When sperm cells are present different chemicals are added at various times in order to separate out the sperm cells from non-sperm cells.

QuantificationThe amount of DNA present is determined for each sample in order to help with the next step. Having the correct amount of DNA to amplify is critical to the final outcome – too little or too much can result in inadequate results.

AmplificationMillions of copies are made of specific locations on the DNA through a process called polymerase chain reaction (PCR). With this process small quantities of DNA can produce results. During PCR, fluorescent tags are incorporated within the copies.

CharacterizationA genetic analyzer is used to detect the fluorescent tags.The data is put into a graph called an electropherogram that is then evaluated by the DNA interpretation analyst.


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The DNA process is targeting specific regions of DNA known as Short Tandem Repeats (STRs) where individuals are known to differ. With STR’s analysts are looking at specific areas of DNA that are repeat sequences and do not code for anything (i.e. an analyst cannot determine ethnicity, height, hair color, health risks, etc.). Analysts are able to make comparisons between reference profiles from known samples and profiles developed from unknown evidence samples.

Unknown Evidence

Known Reference Sample


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In addition to STRs, the DNA section also utilizes Y chromosomal testing or Y-STRs. Y-STRs are short tandem repeats on the Y chromosome. Because only males have a Y chromosome, female DNA does not interfere with Y chromosomal testing. Unlike STR testing, Y-STRs are not unique to each individual. Y-STRs are paternally inherited, meaning that all paternally related males will have the same Y-STR profile.

Biological Father

Son


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CODIS

The Combined DNA Index System (CODIS) is a nationwidedatabase administered by the FBI. It is used for linking serialcrimes and unsolved cases with repeat offenders. CODIS waslaunched in October 1998 and now electronically links all50 states plus 2 federal laboratories and Puerto Rico. Federalguidelines regulate what samples are qualified for entry intoCODIS. Forensic unknown samples must be linked to a crimein order to be eligible for CODIS entry.

Within Arizona there are seven CODIS laboratories. They include the Phoenix PD Crime Lab, Mesa PD Crime Lab, Tucson PD Crime Lab, Scottsdale PD Crime Lab and three DPS laboratories (Phoenix, Tucson, and Flagstaff).

For more information and statistics visit:https://www.fbi.gov/services/laboratory/biometric-analysis/codis

CODIS Success Stories

Sarah Clark CaseOn May 16, 1988, the body of 22-year old Sarah Clark was found in her apartment. She had been brutally raped and murdered. Evidencewas collected and preserved. Potential suspects were ruled out and the case grew cold over time. In June 2001, the Phoenix Police Department’s Cold Case Unit brought Sarah Clark’s caseto the Crime Lab, with the hope that DNA testing and the CODIS database would shed some light on who may have committedthis horrendous crime. A DNA profile was developed from semen taken from Sarah’s sexual assault kit. This unidentified male’s profile was entered into the CODIS database in August 2001. The profile was continuously searched against other forensic samples as well as convicted offender samples for several years – with no luck. On January 13, 2005, a “hit” happened. The unidentified male profile was matched to a convicted offender’s sample that had just been entered into the database. Through a confirmation process, the convicted offender was identified as Mario Pete. Mario Pete was a 16 year old juvenile who lived in Sarah’s apartment complex.


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Further DNA testing was completed on multiple items of evidence that had been collected at the crime scene and sitting silently in the police property facility. A bloody palm print on the wall outside of Sarah’s apartment was compared to Mario Pete and found to match. Mario Pete’s DNA was also present on other items as well, including blood trails leading from Sarah’s apartment and semen on a towel left near Sarah’s body. In March 2007, Mario Pete was put on trial for the rape and murder of Sarah Clark and was convicted within hours. He was sentenced to life in prison in April 2007, coincidentally on his 35th birthday.

Laura Hunding CaseOn July 17, 1989, Laura Hunding’s body was found partially nude, laying in the hallway of her apartment. She was just 27 years old when she was sexually assaulted and stabbed to death in her Phoenix residence. In June 2001, Detective Art Scott of the Phoenix Police Department’s Cold Case Unit brought this case to the Crime Lab for DNA analysis. By August 2001, an unknown male DNA profile was developed from the sexual assault evidence and entered into the DNA database, CODIS. Over a dozen possible suspect samples were collected over the years and compared to this unknown male DNA sample, but none of them matched. In January 2014, nearly a decade and a half after the unknown sample was developed, CODIS produced a match to a convicted offender named Cudellious Love. Additional clothing items Hunding was wearing were subsequently tested and also determined to contain DNA from Love. Twenty five years after Laura Hunding was murdered, the CODIS developed perpetrator, 58 year old Cudellious Love, was arrested. On June 1, 2015, Love was convicted of the first degree murder of Laura Hunding and, despite his pleas of innocence, was subsequently sentenced to life without the possibility of parole for this heinous crime. To date, there is no known connection between Hunding and Love as the two lived quite a distance apart and by all accounts were strangers to one another.

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Documents

Overview DNA CODIS• DNA cannot determine how it was left on the evidence • Sometimes complex mixtures are not interpretable • Limited samples can yield incomplete profiles There